An electrocardiogram (ECG) measures and records electrical potential signals and visually depicts heart electrical activity over time. Conventionally, a standard 12-lead configuration is used in-clinic to record cardiac electrical signals from established chest locations. Physicians use ECGs to diagnose heart problems and other health concerns during appointments; however, spot ECG recording may not always detect sporadic conditions, including conditions affected by fluctuations in blood pressure, blood sugar, respiratory function, temperature, cardiac physiology and pathophysiology, or cardiac rhythm.
Physicians may provide improved diagnoses through ambulatory ECG monitoring that increases the odds of capturing sporadic conditions, during which a subject can also engage in activities of daily living. While long-term extended ambulatory monitoring in-clinic is implausible and impracticable, diagnostic efficacy can be improved through long-term extended ambulatory ECG monitoring. A 30-day observation period is considered the “gold standard,” but has heretofore proven unworkable because existing ECG monitoring systems have been arduous to employ, cumbersome to the patient, and expensive.
Extended ECG monitoring is further complicated by patient intolerance to long-term electrode wear and predisposition to skin irritation. Moreover, natural materials from the patient's body, such as hair, sweat, skin oils, and dead skin cells, can get between an electrode, adhesives, and the skin's surface, which can adversely affect electrode contact and cardiac signal recording quality. Patient physical movement and clothing can impart forces on the ECG electrode contact point; inflexibly fastened ECG electrodes are particularly prone to becoming dislodged. Precisely re-placing a dislodged ECG electrode may be essential to ensuring signal capture at the same fidelity. Dislodgment may occur unbeknownst to the patient, rendering the ECG recordings worthless.
The high cost of the patient-wearable components used to provide long-term extended ECG monitoring can also negatively influence the availability and use of monitors. Disposable components, such as adhesive electrodes, ideally should be inexpensive, while more complex components, particularly the electronic hardware that detects and records ECG and related physiological data, may be unavoidably expensive. Costs can be balanced by designing the electric hardware to be re-usable, but when the total cost of a full ECG monitoring ensemble remains high, despite the utilization of re-usable parts, the number of monitors available for use by healthcare providers can be inhibited. Cost, then, becomes a barrier to entry, which, in turn, can hinder or prevent healthcare providers from obtaining the means with which to efficaciously identify the physiology underlying sporadic cardiac arrhythmic conditions and can ultimately contribute to a failure to make proper and timely medical diagnose.
ECG data are crucial for diagnosing many cardiovascular conditions. For example, detecting abnormal respiratory function with ECG data showing normal respiratory variation may facilitate diagnosis, prognosis, and treatment of certain disorders. Moreover, ECG data obtained through ambulatory monitoring, when combined with additional physiological data, can be especially helpful when diagnosing athletes, who present unique concerns not generally observed in a non-physically active patient population. For example, blood sugar plays a strong role in athletic performance and recovery and correlates with cardiac function. Monitoring respiratory and ECG together can help in diagnosing cardiorespiratory conditions common to athletes, especially since such conditions not only impair performance, but when combined with overtraining, a cardiorespiratory impairment may lead to severe or even terminal conditions, including severe bronchoconstriction or sudden death.
Existing portable devices that monitor cardiac data and other physiological data, at best, provide suboptimal results. Such devices can be inconvenient and may restrain movement; for example, a Holter device, which is a wearable ECG monitor with leads placed in a similar position as used with a standard ECG set-up, is cumbersome, expensive, typically only available by medical prescription, and requires skilled medical staff to properly position the electrodes.
Wrist monitors, such as the Fitbit product line of activity trackers, manufactured by Fitbit Inc., San Francisco, Calif., and related technologies, like wristwatch smartphones (also known as smartwatches), such as the Apple Watch, manufactured by Apple Inc., Cupertino, Calif. or the Gear S smartwatch, manufactured by Samsung Electronics Co., Ltd., Suwon, South Korea, as well as clothing embedded with sensors, such as the Hexoskin product line of wearable clothing, manufactured by Carré Technologies, Inc., Montreal, Quebec, Canada, all experience fidelity problems related to variation in electrode and sensor contact. Gaps in signal quality or interruptions or distortions of the data stream can lead to false positives and false negatives critical to understanding the relationship between physiological markers and medical events or needs.
U.S. Pat. No. 8,668,653, to Nagata, et al., discloses an ECG-monitoring shirt with a plurality of electrodes, including four limb electrodes and sensors disposed on a beltline. To fit each of the electrodes on the body surface of the examinee, a low-irritant acrylic adhesive, for example, may be applied on each of the electrodes that fit on the body's surface. The use of adhered electrodes is incompatible in patients with a predisposition to skin irritation.
Therefore, a need remains for an ambulatory, extended-wear monitor that can be used by patients who are intolerant to adhesively-adhered electrodes; highly mobile individuals, such as athletes, whose movement will cause adhesively-adhered electrodes to become dislodged; and individuals of all types in whom the recording high-quality PQRSTU ECG data and related physiological data are desired.